A drive recorder is mounted on a vehicle such as an automobile that may travel on the road, and records video captured by a camera directed forward with respect to the vehicle. Images captured by the camera are recorded on a detachable recording medium, such as a memory card. If an image recorded on the memory card is stored in an external device (e.g. server), operations such as detaching of the memory card from the drive recorder are necessary. Such operations represent a burden on the driver of the vehicle.
In view of this, drive recorders have been proposed that identify a time point at which an acceleration above a predetermined threshold was detected and transmit to the server images captured during a predetermined time period associated with that point. The detected acceleration indicates the strength of an impact applied to the drive recorder. However, such a drive recorder must transmit images each time an acceleration above a predetermined value is detected. This results in very large amounts of transmission, requiring high transmission costs.
Patent Document 1 discloses a vehicle-mounted recorder mounted on a railway vehicle which, in response to a request from a command center, transmits video captured when an application of the emergency brake was detected.
The vehicle-mounted recorder according to Patent Document 1 is installed on the lead vehicle of a train and records video of a scene in the direction of advance of the train. When the vehicle-mounted recorder detects emergency braking based on the acceleration measured by the acceleration meter, it notifies the command center of an occurrence of emergency braking. To prevent the video ending at the time point of the detection of emergency braking of the train and starting at the time point going back a predetermined time period (also known as emergency-braking imagery) from being deleted, the vehicle-mounted recorder changes the storage region for video recording from the region that has been used until the emergency braking was detected over to another recording region.
When a train has applied the emergency brake, the operator at the command center contacts the driver of the train to determine whether to check the video captured upon the application of the emergency brake. When the operator determines that he needs to check the video, he requests the vehicle-mounted recorder to transmit images captured upon the application of the emergency brake. In response to the request from the command center, the vehicle-mounted recorder transmits emergency braking images to the command center.
In the context of an automobile, the number of times that an acceleration that would correspond to railway emergency braking is detected is overwhelmingly larger than at a train. If the vehicle-mounted recorder according to Patent Document 1 is mounted on an automobile, it is not realistic that the vehicle administrator determines whether images need to be stored each time he is notified of an application of the emergency brake. In the context of a drive recorder mounted on a vehicle travelling on the road, such as an automobile, it is desirable that images captured when operations such as sudden braking were done be checked afterward and used to help manage the vehicle operation.
Patent Document 1 describes a situation where the train driver applies the emergency brake and discusses the problem of how the command center can accurately and quickly learn how the application of the emergency brake happened at the train, while reducing the burden on the driver. That is, the vehicle-mounted recorder according to Patent Document 1 does not contemplate checking past conditions of the emergency braking, making it impossible to acquire images relating to past emergency braking from the vehicle-mounted recorder.